quick OpenCV detect question

djdune

in Contributed Library Questions • 2 years ago

When using detect, if no recognizable object is within the window, what does a call to open.detect() return? If you know the answer, read no more, I'm just going to detail my thought process.

I have my code set so the x-y of the rectangle are printed. The confusing behavior I'm seeing is that when i duck my head to the side of the screen, the print messages simply stop coming. What is happening here?

detect() is of type Rectangle, no? calling faces[i].isEmpty() returns false when there is a face, but i can't seem to get it to return true. here's a link to the Java API if that helps.

I expected to find a detect method in the OpenCV.java file, but instead just find this at the very end.

public native Rectangle[] detect( float scale, int min_neighbors, int flags, int min_width, int min_height );
public Rectangle[] detect() {
return detect( 1.1f, 3, 0, 0, 0 );
}

Maybe it's somewhere in the OpenCV frameworks files, but I can't track it down. I have little practical programming experience of this sort. What's goin on? Here is the code I'm using to troubleshoot.

import hypermedia.video.*;
import java.awt.Rectangle;
OpenCV opencv;
void setup() {
size( 320, 240 );
opencv = new OpenCV(this);
opencv.capture( width, height );
opencv.cascade( OpenCV.CASCADE_FRONTALFACE_ALT ); // load the FRONTALFACE description file
}
void draw() {
opencv.read();
image( opencv.image(), 0, 0 );
// detect anything ressembling a FRONTALFACE
Rectangle[] faces = opencv.detect(1.2, 3, OpenCV.HAAR_DO_CANNY_PRUNING, 20, 20);
// draw detected face area(s)
noFill();
stroke(255,0,0);
for( int i=0; i<faces.length; i++ ) {
rect( faces[i].x, faces[i].y, faces[i].width, faces[i].height );
rect( faces[i].x + 0.5*faces[i].width, faces[i].y + 0.34*faces[i].height, 5, 5 );
if (!faces[i].isEmpty())
{
println("there is a face");
}
//never enters
if (faces[i].width == 0)
{
println("zero w");
}
print("(" + faces[i].x + "," + faces[i].y + ") ");
println("w: " + faces[i].width + ", h: " + faces[i].height);
}
}